青海木里煤田聚乎更矿区煤中稀土元素地球化学特征及其对成煤环境的指示

    Geochemistry characteristics and indicative significance of rare earth elements in coal from Juhugeng coal district, the Muli coalfield in Qinghai Province

    • 摘要: 运用高分辨电感耦合等离子质谱(ICP-MS)、X射线荧光光谱、光学显微镜及煤的工业分析对聚乎更矿区主采煤层下1煤层及其顶底板中的稀土元素、主量元素、显微组分及工业组分进行测定,分析稀土元素的含量、地球化学特征和分布模式对成煤环境的指示。结果表明:聚乎更矿区下1煤中稀土元素平均含量为23.01×10-6,相对不富集;LREE/HREE平均值为3.38;表明轻稀土元素较重稀土元素富集;下1煤层顶底板泥岩中,稀土元素相对富集,稀土元素总量远高于煤中,均值为煤中的8.6倍,轻稀土元素明显富集。顶底板与煤中稀土元素分配模式相似,受煤炭堆积沼泽水体变化和后期热液作用的影响,稀土元素含量有轻微的分异,煤中稀土元素与陆源岩关系密切。煤中δEu负异常明显,结构保存指数与凝胶化指数图解显示成煤环境主要为还原环境,与Eu异常指示的成煤环境一致。Ce呈现负异常,可能与其处于强的还原环境有关。煤中稀土元素与灰分呈中等正相关关系,与SiO2呈正相关关系,表明聚乎更矿区下1煤中稀土元素呈无机态赋存。煤层顶底板泥岩中稀土元素含量与粘土矿物呈明显的正相关关系,其中伊利石含量与稀土元素富集关系最密切。

       

      Abstract: The rare earth elements, major elements, microcomponents and industrial components in the coal seam and its roof and floor were determined by ICP-MS, X-ray fluorescence spectrum, optical microscope and industrial analysis of coal.According to the results, the content, geochemical characteristics and distribution patterns of rare earth elements were comprehensively analyzed.The modes of occurrence and genesis of rare earth elements in coal were discussed.The results show that the average content of REE is 23.01×10-6 in the No.1 coal of the Juhugeng mining area.LREE/HREE mean value is 3.38, indicating that the light rare earth elements are more abundant than the heavy rare earth elements.In the top and bottom mudstone of the lower coal, rare earth elements are relatively enriched, and the total amount of rare earth elements is much higher than that of coal, with an average value of 8.6 times that of coal.The distribution mode of rare earth elements in the roof and floor is similar to that in the coal.With the influence of the change of water body in the coal accumulation swamp and the later hydrothermal action, the rare earth content is slightly different.The rare earth elements in the coal are closely related to the continental source rocks.In the coal, Eu negative anomaly is obvious, and the structure preservation index (TPI) versus gelation index (GI) diagram shows that the coal-forming environment is mainly a reducing environment, which is consistent with the coal-forming environment indicated by Eu anomaly.The negative Ce anomaly may be related to the strong reduction environment.In coal, rare earth element REE is positively correlated with ash content (R=0.481), and positively correlated with SiO2 (R=0.652), indicating that rare earth elements in the No.1 coal in the Juhugeng mining area coexist in inorganic state.The content of rare earth elements in the mudstone of roof and floor is positively correlated with clay minerals, among which the content of illite is most closely related to the enrichment of rare earth elements.

       

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